Inspection method, inspection device, and marking forming method

ABSTRACT

An inspection method according to an embodiment is an inspection method of performing laser marking on a semiconductor device including a substrate and a metal layer formed on the substrate, and the inspection method includes specifying a fault point in the semiconductor device by inspecting the semiconductor device, and irradiating the semiconductor device with laser light having a wavelength that is transmitted through the substrate from the substrate side so that a marking is formed at least at a boundary between the substrate and the metal layer on the basis of the fault point.

TECHNICAL FIELD

An aspect of the present invention relates to a semiconductor deviceinspection method, an inspection device, and a marking forming method.

BACKGROUND ART

As a technique of inspecting a semiconductor device, there is atechnique of performing marking through irradiation with laser light atseveral places around a fault point when a fault point has beenspecified. Such a technique is a highly effective technique because thetechnique allows a fault point to be readily ascertained using markingin a post-process in fault analysis.

In a case in which marking is performed on, for example, a packagedsample (a semiconductor device), and a sample in which it is necessaryto use a probe card without a window on the metal layer side, the samplecannot be irradiated with laser light from the front surface side (themetal layer side), and therefore, it is necessary to irradiate thesample with laser light from the back surface side (the substrate side).For example, Patent Literature 1 discloses a fault analysis device thatanalyzes a fault position in a semiconductor device in which an SiCsubstrate is used, using an optical beam induced resistance change(OBIRCH) method. Patent Literature 1 discloses that irradiation isperformed with laser light from the back surface side and laser markingis performed on a device and a circuit on the front surface side of thesubstrate.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Publication No.2012-97391

SUMMARY OF INVENTION Technical Problem

However, Patent Literature 1 does not disclose a detailed position ofthe marking. Further, when physical analysis of a semiconductor deviceis performed on the basis of the marking, a position of the marking maybe confirmed from the front surface side or the position of the markingmay be confirmed from the back surface side. Therefore, it is preferablefor a position at which the marking is formed to be a position that canbe easily confirmed from both the front surface side and the backsurface side.

Therefore, an object of an aspect of the present invention is to providean inspection method capable of allowing a marking position to beconfirmed from both the front surface side and the back surface side atthe time of physical analysis when laser marking is performed from asubstrate side of a semiconductor device, an inspection device, and amarking forming method.

Solution to Problem

An inspection method according to an aspect of the present invention isan inspection method of performing laser marking on a semiconductordevice including a substrate and a metal layer formed on the substrate,the inspection method including: specifying a predetermined position inthe semiconductor device by inspecting the semiconductor device; andirradiating the semiconductor device with laser light having awavelength that is transmitted through the substrate from the substrateside so that a marking is formed at least at a boundary between thesubstrate and the metal layer on the basis of the predeterminedposition.

In this inspection method, the semiconductor device is irradiated withlaser light having a wavelength transmitted through the substrate fromthe substrate side so that the marking is formed at least at theboundary between the substrate and the metal layer on the basis of apredetermined position (for example, a fault point) specified in thesemiconductor device. It is possible to form the marking at a positionat which the marking can be easily confirmed from both the front surfaceside (the metal layer side) and the back surface side (the substrateside) by forming the marking at the boundary between the substrate andthe metal layer. Accordingly, when laser marking is performed from thesubstrate side of the semiconductor device, it is possible to easilyconfirm the marking position from both the front surface side and theback surface side at the time of physical analysis.

The irradiating the semiconductor device with laser light may includecontrolling the irradiation with laser light so that the marking doesnot penetrate the metal layer. Accordingly, the marking can be keptinside the semiconductor device. As a result, it is possible to preventthe front surface of the semiconductor device from being contaminateddue to debris of the semiconductor device that may be generated at thetime of marking formation.

The irradiating the semiconductor device with laser light may includecontrolling the irradiation with the laser light so that at least one ofcavities, reforming, and melting is generated as the marking.Accordingly, it is possible to appropriately form the marking.

The inspection method may further include acquiring a pattern image ofthe semiconductor device including a mark image indicating the marking.Accordingly, it is possible to acquire a pattern image from which themarking position can be visually ascertained together with the pattern(for example, a wiring pattern) of the semiconductor device. With such apattern image, it becomes possible to easily ascertain the markingposition in the physical analysis.

The inspection method may further include acquiring position informationfor specifying a position of the marking on the basis of the patternimage; and outputting the position information. Accordingly, it ispossible to output the marking position information for specifying themarking position in the physical analysis to an external device or thelike. Therefore, for example, even in a case in which the inspectiondevice that performs marking and the analysis device that performsphysical analysis are disposed in different places, it is possible toappropriately transfer the marking position information necessary toperform physical analysis to the analysis device.

The acquiring the position information may include acquiring informationindicating a relative position of the marking with reference to afeature point of the semiconductor device as the position information.It is possible to accurately ascertain the position of the marking byusing the relative position of the marking with respect to a position ofthe feature point (for example, a groove portion of a wiring pattern) ofthe semiconductor device as position information.

The inspection method may further include thinning the substrate afterthe irradiating the semiconductor device with the laser light, andobserving the semiconductor device from the thinned substrate side. Itis possible to easily confirm the position of the marking in theobservation step by thinning the substrate. Accordingly, it is possibleto accurately perform the physical analysis on the basis of the positionof the marking.

An inspection device according to an aspect of the present invention isan inspection device that performs laser marking on a semiconductordevice including a substrate and a metal layer formed on the substrate,the inspection device including: an observation optical systemconfigured to transfer light from the substrate side of thesemiconductor device; a photodetector configured to detect light fromthe semiconductor device via the observation optical system and output adetection signal; a laser light source configured to output laser lighthaving a wavelength that is transmitted through the substrate; a markingoptical system configured to irradiate the semiconductor device with thelaser light output by the laser light source from the substrate side;and a marking control unit configured to control an output of the laserlight source so that a marking is formed at least on a boundary betweenthe substrate and the metal layer on the basis of a predeterminedposition that is specified on the basis of the detection signal.

In this inspection method, the semiconductor device is irradiated withlaser light having a wavelength transmitted through the substrate fromthe substrate side so that the marking is formed at least at theboundary between the substrate and the metal layer on the basis of apredetermined position (for example, a fault point) specified in thesemiconductor device. It is possible to form the marking at a positionat which the marking can be easily confirmed from both of the frontsurface side (the metal layer side) and the back surface side (thesubstrate side) by forming the marking at the boundary between thesubstrate and the metal layer. Accordingly, when laser marking isperformed from the substrate side of the semiconductor device, it ispossible to easily confirm the marking position from both the frontsurface side and the back surface side at the time of physical analysis.

The marking control unit may control an output of the laser light sourceso that the marking does not penetrate through the metal layer.Accordingly, the marking can be kept inside the semiconductor device. Asa result, it is possible to prevent the front surface of thesemiconductor device from being contaminated due to debris of thesemiconductor device that may be generated at the time of markingformation.

The marking control unit may control an output of the laser light sourceso that at least one of cavities, reforming, and melting is generated asthe marking. Accordingly, it is possible to appropriately form themarking.

The inspection device may further include a processing unit configuredto acquire a pattern image of the semiconductor device including a markimage indicating the marking on the basis of the detection signal.Accordingly, it is possible to acquire a pattern image from which themarking position can be visually ascertained together with the pattern(for example, a wiring pattern) of the semiconductor device. With such apattern image, it becomes possible to easily ascertain the markingposition in the physical analysis.

The processing unit may acquire position information for specifying theposition of the marking on the basis of the pattern image, and outputthe position information. Accordingly, it is possible to output themarking position information for specifying the marking position in thephysical analysis to an external device or the like. Therefore, forexample, even in a case in which the inspection device that performsmarking and the analysis device that performs physical analysis aredisposed in different places, it is possible to appropriately transferthe marking position information necessary to perform physical analysisto the analysis device.

The processing unit may acquire information indicating a relativeposition of the marking with reference to a feature point of thesemiconductor device as the position information. It is possible toaccurately ascertain the position of the marking by using the relativeposition of the marking with respect to the position of the featurepoint (for example, a groove portion of a wiring pattern) of thesemiconductor device as position information.

A marking forming method according to an aspect of the present inventionis a marking forming method of performing laser marking on asemiconductor device including a substrate and a metal layer formed onthe substrate, the marking forming method including: irradiating thesemiconductor device with laser light having a wavelength that istransmitted through the substrate from the substrate side so that amarking is formed at least at a boundary between the substrate and themetal layer with respect to a predetermined position of thesemiconductor device.

In this marking for method, the semiconductor device is irradiated withlaser light having a wavelength transmitted through the substrate fromthe substrate side so that the marking is formed at least at theboundary between the substrate and the metal layer. It is possible toform the marking at a position at which the marking can be easilyconfirmed from both the front surface side (the metal layer side) andthe back surface side (the substrate side) by forming the marking at theboundary between the substrate and the metal layer. Accordingly, whenlaser marking is performed from the substrate side of the semiconductordevice, it is possible to easily confirm the marking position from boththe front surface side and the back surface side at the time of physicalanalysis.

The irradiating the semiconductor device with the laser light mayinclude controlling the irradiation with the laser light so that themarking does not penetrate the metal layer. Accordingly, the marking canbe kept inside the semiconductor device. As a result, it is possible toprevent the front surface of the semiconductor device from beingcontaminated due to debris of the semiconductor device that may begenerated at the time of marking formation.

The irradiating the semiconductor device with the laser light mayinclude controlling the irradiation with the laser light so that atleast one of cavities, reforming, and melting is generated as themarking. Accordingly, it is possible to appropriately form the marking.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible toprovide an inspection method capable of allowing a marking position tobe easily confirmed from both the front surface side and the backsurface side at the time of physical analysis when laser marking isperformed from a substrate side of a semiconductor device, an inspectiondevice, and a marking forming method.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram of an inspection device according toan embodiment of the present invention.

A portion (a) of FIG. 2 is a diagram illustrating an example of apattern image with a low magnification, a portion (b) of FIG. 2 is adiagram illustrating an example of a pattern image with a mediummagnification, and a portion (c) of FIG. 2 is a diagram illustrating anexample of a pattern image with a high magnification.

A portion (a) of FIG. 3 is a diagram illustrating an example of ananalysis image and a portion (b) of FIG. 3 is a diagram illustrating anexample of a reference image.

FIG. 4 is a schematic cross-sectional view of a laser markedsemiconductor device.

FIG. 5 is a diagram illustrating marking position information that isgenerated by an inspection device.

FIG. 6 is a flowchart illustrating an example of an operation of theinspection device.

FIG. 7 is a diagram illustrating a configuration example of asemiconductor device, in which a portion (a) illustrates a schematiccross section of a logic device and a portion (b) illustrates aschematic cross section of a memory device.

FIG. 8 is a diagram illustrating an example of a semiconductor device,in which a portion (a) illustrates a schematic cross section of a powerdevice and a portion (b) illustrates a bottom surface of a power device.

FIG. 9 is a diagram illustrating a state after a substrate of the powerdevice in FIG. 8 is thinned, in which a portion (a) illustrates aschematic cross section of the power device, and a portion (b)illustrates a bottom surface of the power device.

A portion (a) of FIG. 10 is a diagram illustrating an example of animage with a low magnification obtained by imaging a cross-sectionalportion including a marking in a semiconductor device using an SEM, anda portion (b) of FIG. 10 is a diagram illustrating an example of animage with a high magnification obtained by imaging a cross-sectionalportion including a marking in a semiconductor device using an SEM.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Itshould be noted that in the description of the drawings, the same orcorresponding elements are denoted by the same reference numerals, andredundant description is omitted.

As illustrated in FIG. 1, an inspection device 1 according to theembodiment is a device for inspecting a semiconductor device D which isa device under test (DUT), such as specifying a fault point (apredetermined position) in the semiconductor device D. Morespecifically, the inspection device 1 specifies a fault point andperforms marking indicating the fault point around the fault point. Withthis marking, it is possible to easily ascertain the fault pointspecified by the inspection device 1 in a post-process (physicalanalysis) of fault analysis.

Examples of the semiconductor device D include a discrete semiconductorelement (discrete), an optoelectronic element, a sensor/actuator, alogic large scale integration (LSI), a memory element, a linearintegrated circuit (IC), and a combination thereof. The discretesemiconductor elements include a diode, a power transistor, or the like.The logic LSI includes a transistor having a metal-oxide-semiconductor(MOS) structure, a bipolar transistor, or the like. Further, thesemiconductor device D may be a package including a semiconductordevice, a composite substrate, or the like. The semiconductor device Dincludes a substrate, and a metal layer formed on the substrate. As thesubstrate of the semiconductor device D, for example, a siliconsubstrate is used. The semiconductor device D is placed on a samplestage 40.

The inspection device 1 performs a fault point specifying process forspecifying a fault point of the semiconductor device D, and a markingprocess for performing marking indicating the fault point around thespecified fault point. The inspection device 1 includes a stimulationdevice 11, a light source 12, an optical system 13 including anobservation optical system 13A and a marking optical system 13B, an XYZstage 14, a photodetector 15, a laser light source 16, a computer 21, adisplay unit 22, and an input unit 23.

First, functional configurations of the inspection device 1 related tothe fault point specifying process will be described. The inspectiondevice 1 includes a stimulation device 11, a light source 12, anobservation optical system 13A, an XYZ stage 14, a photodetector 15, acomputer 21, a display unit 22, and an input unit 23 as functionalconfigurations related to the fault point specifying process.

The stimulation device 11 functions as a stimulation signal applicationunit that is electrically connected to the semiconductor device D via acable and applies a stimulation signal to the semiconductor device D.The stimulation device 11 is, for example, a pulse generator thatapplies a stimulation signal to the semiconductor device D, a testerunit that inputs a test signal, and so on. The stimulation device 11 isoperated by a power supply (not illustrated) and repeatedly applies astimulation signal such as a predetermined test pattern to thesemiconductor device D. The stimulation device 11 may be a stimulationdevice that applies a modulated current signal or may be a stimulationdevice that applies a direct current signal. The stimulation device 11is electrically connected to the computer 21 via a cable and applies astimulation signal such as a test pattern designated from the computer21 to the semiconductor device D. It should be noted that thestimulation device 11 may not necessarily be electrically connected tothe computer 21. When the stimulation device 11 is not electricallyconnected to the computer 21, the stimulation device 11 determines astimulation signal such as a test pattern alone and applies thestimulation signal such as a test pattern to the semiconductor device D.

The light source 12 is operated by a power supply (not illustrated) andoutputs light for illuminating the semiconductor device D. The lightsource 12 is a light emitting diode (LED), a lamp light source, or thelike. A wavelength of the light output from the light source 12 is awavelength that is transmitted through the substrate of thesemiconductor device D. For example, when the substrate of thesemiconductor device D is silicon, the wavelength is preferably 1064 nmor more. The light output from the light source 12 is guided to theobservation optical system 13A.

The observation optical system 13A is an optical system that guideslight from the substrate side of the semiconductor device D to thephotodetector 15. The observation optical system 13A may be configuredto be combined with the marking optical system 13B to be described belowor may be configured separately from the marking optical system 13B. Theobservation optical system 13A irradiates the semiconductor device Dwith the light output from the light source 12 from the substrate sideof the semiconductor device D, that is, the back surface D1 side of thesemiconductor device D. For example, the observation optical system 13Aincludes a beam splitter and an objective lens. The objective lensconverges the light output from the light source 12 and guided by thebeam splitter to an observation area. For example, the observationoptical system 13A is placed on the XYZ stage 14. The XYZ stage 14 ismovable in a Z-axis direction, and an X-axis direction and a Y-axisdirection orthogonal to the Z-axis direction when an optical axisdirection of the objective lens is the Z-axis direction. The XYZ stage14 is movable in the three axis directions described above by beingcontrolled by a control unit 21 b (to be described below) of thecomputer 21. The observation area is determined by a position of the XYZstage 14.

The observation optical system 13A transfers light (reflected light)transmitted through the substrate of the semiconductor device D andreflected by the semiconductor device D in accordance with illuminationlight to the photodetector 15. Specifically, the light radiated from theobservation optical system 13A is transmitted through the substrate SiE(see FIG. 4) of the semiconductor device D and is reflected by the metallayer ME (see FIG. 4). The light reflected by the metal layer ME istransmitted through the substrate SiE again and input to thephotodetector 15 via the objective lens and the beam splitter of theobservation optical system 13A. In addition, the observation opticalsystem 13A transfers the light generated in the semiconductor device Ddue to the application of the stimulation signal to the photodetector15. Specifically, light (for example, emission light) generated in themetal layer ME of the semiconductor device D mainly due to theapplication of the stimulation signal is transmitted through thesubstrate SiE and is input to the photodetector 15 via the objectivelens and the beam splitter of the observation optical system 13A.

The photodetector 15 images the light from the semiconductor device Dand outputs image data (a detection signal). For example, thephotodetector 15 images light reflected from the semiconductor device D,and outputs image data for generating a pattern image. It is possible toascertain a marking position on the basis of the pattern image. Further,the photodetector 15 images the emission light from the semiconductordevice D and outputs image data for generating an emission image. Anemission point in the semiconductor device D can be specified on thebasis of the emission image. It is possible to specify the fault pointof the semiconductor device D by specifying the emission point. Forexample, a camera in which a charge coupled device (CCD) image sensor ora complementary metal oxide semiconductor (CMOS) image sensor capable ofdetecting light having a wavelength transmitted through the substrateSiE of the semiconductor device D is mounted, an InGaAs camera, or atwo-dimensional camera such as an MCT camera is used as thephotodetector 15 that measures the emission light.

The computer 21 is electrically connected to the photodetector 15 or thelike via a cable. The computer 21 is, for example, a computer includinga processor (CPU: Central Processing Unit), a random access memory(RAM), a read only memory (ROM), a solid state drive (SSD), a hard diskdrive (HDD) that are storage media, and the like. The computer 21executes a process of the processor for data stored in the storagemedium. The computer 21 generates a pattern image and an emission imageon the basis of the image data input from the photodetector 15. Thepattern image is an image captured so that a circuit (for example, acircuit pattern formed on the metal layer ME) of the semiconductordevice D can be confirmed. It should be noted that a cloud server, asmart device (for example, a smartphone or a tablet terminal), amicrocomputer, a field-programmable gate array (FPGA), or the like maybe used for the computer 21.

As illustrated in FIG. 2, the computer 21 acquires pattern images ofrespective magnifications from a low magnification to a highmagnification with respect to a portion including an emission point inthe semiconductor device D. A portion (a) of FIG. 2 illustrates apattern image A1 with a low magnification, a portion (b) of FIG. 2illustrates a pattern image A2 with a medium magnification, and aportion (c) of FIG. 2 illustrates a pattern image A3 with a highmagnification. For example, the computer 21 can acquire the patternimages A1 to A3 according to the respective magnifications bycontrolling the objective lens of the observation optical system 13A.

Here, it is difficult to specify the emission position in the pattern (acircuit pattern or the like) of the semiconductor device D with only theemission image described above. Therefore, the computer 21 generates, asan analysis image, a superimposed image in which the pattern imagegenerated as described above and the emission image based on theemission light from the semiconductor device D are superimposed. Aportion (a) of FIG. 3 illustrates an analysis image A4 in which thepattern image A3 with a high magnification and an emission image showingthe fault point fp which is an emission point are superimposed.

The computer 21 outputs the analysis image A4 to the display unit 22.The display unit 22 is a display device such as a display for showingthe analysis image A4 or the like to the user. The display unit 22displays the input analysis image A4. In this case, a user confirms theposition of the fault point fp from the analysis image A4 displayed onthe display unit 22, and inputs information indicating the fault pointfp to the input unit 23. The input unit 23 is an input device such as akeyboard and a mouse that receive an input from the user. The input unit23 outputs information indicating the fault point fp received from theuser to the computer 21. The computer 21, the display unit 22, and theinput unit 23 may form a tablet terminal. The above is a description ofa functional configuration of the inspection device 1 related to thefault point specifying process.

Next, a functional configuration of the inspection device 1 related tothe marking process will be described. The marking process is a processof performing marking indicating a fault point fp specified through thefault point specifying process, around the fault point fp.

The inspection device 1 further includes a laser light source 16 and amarking optical system 13B, in addition to the respective functionalconfigurations related to the fault point specifying process describedabove, as a functional configuration related to the marking process.Further, the computer 21 includes a condition setting unit 21 a, acontrol unit 21 b (a marking control unit), and an analysis unit 21 c (aprocessing unit).

In the marking process, laser marking is performed on the basis of thefault point fp (predetermined position) specified in the fault pointspecifying process. As illustrated in a portion (b) of FIG. 3 and FIG.4, a marking point mp is set around the fault point fp (here, fourpoints in this example). In the marking process, the marking point mp ofthe semiconductor device D is irradiated with the laser light output bythe laser light source 16 via the marking optical system 13B. That is,the marking point mp is irradiated from the substrate SiE side of thesemiconductor device D with laser light having a wavelength that istransmitted through the substrate SiE. Accordingly, a marking is formedat a boundary between the substrate SiE and the metal layer ME.Hereinafter, a functional configuration of the inspection device 1related to the marking processing will be described in detail.

The condition setting unit 21 a sets the marking point mp on the basisof information indicating the fault point fp input from the input unit23. The marking points mp may be set at several points around thespecified fault point fp. The several points are, for example, fourpoints. For example, when information indicating the fault point fp isinput, the condition setting unit 21 a automatically sets the markingpoints mp around the fault point fp at four points around the faultpoint fp. Specifically, for example, in a plan view, the marking pointsmp may be set in a cross shape around the failure portion fp. It shouldbe noted that the marking point mp may be set by the input unit 23receiving an input of information indicating the marking point mp fromthe user who has viewed the analysis image displayed on the display unit22. In this case, the condition setting unit 21 a sets the marking pointmp on the basis of the information indicating the marking point mp inputfrom the input unit 23 instead of automatically setting the markingpoint mp. The condition setting unit 21 a generates a reference image A5(see a portion (b) of FIG. 3) in which marks indicating the fault pointfp and the marking point mp are added to the analysis image A4, andstores the reference image A5 in the computer 21.

The control unit 21 b of the computer 21 moves the XYZ stage 14 in threeaxis directions by controlling the XYZ stage 14. Specifically, thecontrol unit 21 b moves the XYZ stage 14 on which the marking opticalsystem 13B is placed so that laser marking is performed on the markingpoint mp set by the condition setting unit 21 a. When there are aplurality of marking points mp, the control unit 21 b performs controlso that laser marking is sequentially performed on all the markingpoints mp. That is, when the laser marking at one marking point mp iscompleted, the control unit 21 b moves the XYZ stage 14 so that lasermarking of the next marking point mp is performed. When the movement ofthe XYZ stage 14 is completed, the control unit 21 b outputs an outputstart signal to the laser light source 16.

The laser light source 16 is operated by a power supply (notillustrated), and outputs laser light with which the semiconductordevice D is irradiated. When the output start signal is input by thecontrol unit 21 b, the laser light source 16 starts output of laserlight. As the laser light source 16, for example, a semiconductor laseror a fiber laser can be used. A wavelength of the laser light outputfrom the laser light source 16 may be in any wavelength range that istransmitted through the substrate SiE. For example, when the substrateSiE is silicon, the wavelength is preferably 1064 nm or more.

The marking optical system 13B irradiates the marking point mp of thesemiconductor device D from the substrate SiE side of the semiconductordevice D, that is, the back surface D1 side of the semiconductor deviceD with the laser light output from the laser light source 16. Themarking optical system 13B has an objective lens. The objective lenscondenses the laser light from the laser light source 16 at the markingpoint mp. The marking optical system 13B is placed on the XYZ stage 14.The XYZ stage 14 is controlled by the control unit 21 b to be movable inthe three axis directions described. It is to be noted that the markingoptical system 13B may include an optical scanning unit (for example, anoptical scanning element such as a galvanometer mirror, a polygonmirror, and an MEMS mirror) instead of the XYZ stage 14 described above,as a configuration for changing the irradiation position of the laserlight. In this case, the control unit 21 b can control the irradiationposition of the laser light by controlling an operation of the opticalscanning unit. Further, the marking optical system 13B may include ashutter, and the shutter may be operated under the control of thecontrol unit 21 b to pass or block the laser light from the laser lightsource 16 such that the output of the laser light is controlled.

The control unit 21 b is electrically connected to the laser lightsource 16 and controls irradiation with laser light in laser marking.Specifically, the control unit 21 b controls the output of the laserlight source 16 so that the marking is formed at the boundary betweenthe substrate SiE and the metal layer ME. Preferably, the control unit21 b controls the output of the laser light source 16 so that themarking does not penetrate through the metal layer ME. Accordingly, themarking can be kept inside the semiconductor device D. As a result, itis possible to prevent the front surface D2 of the semiconductor deviceD from being contaminated due to debris of the semiconductor device thatmay be generated at the time of marking formation. For example, thecontrol unit 21 b performs control so that the power of the laser lightin laser marking becomes 10 μJ to 10 mJ. In a case in which the laserlight output from the laser light source 16 is a pulse laser, thecontrol unit 21 b may define the number of irradiations of the markingpoint mp with the laser pulse (for example, 50 to 1000 shots) as anirradiation condition of the laser light, thereby controlling theirradiation of the laser light. Further, in a case in which the laserlight output from the laser light source 16 is a continuous wave laser(CW laser), the control unit 21 b may define a time to irradiate themarking point mp with the laser light as an irradiation condition of thelaser light, thereby controlling the irradiation of the laser light.

When the irradiation with the laser light on the basis of theirradiation conditions defined as described above is completed, thecontrol unit 21 b outputs an output stop signal to the laser lightsource 16. When the output stop signal is input, the laser light source16 stops the output of the laser light. Therefore, the laser lightsource 16 outputs the laser light from a point of time that the outputstart signal is input from the control unit 21 b to a point of time thatthe output stop signal is input from the control unit 21 b.

The marking formed due to the irradiation with the laser light may be amarking that can be confirmed by the photodetector 15 or the like, andvarious forms are conceivable. Examples of the marking may includecavities generated due to the irradiation with the laser light,amorphousness generated due to reforming, and a part of the metal layerME or the substrate SiE melted by heat generated due to laser lightabsorbed by the metal layer ME.

After it is confirmed that the marking is appropriately formed at onemarking point mp, the control unit 21 b performs control so that lasermarking of the next marking point nip is started. For example, thecontrol unit 21 b stops the output of the laser light source 16 afterlaser marking at one marking point mp (that is, irradiation with thelaser light based on the set irradiation conditions of the laser light)is completed, performs switching from the marking optical system 13B tothe observation optical system 13A, and starts the output of the lightsource 12. Accordingly, the photodetector 15 images the light from thelight source 12 reflected from the semiconductor device D, and outputsthe image data (the detection signal) described above to the analysisunit 21 c of the computer 21. The analysis unit 21 c generates a patternimage on the basis of the image data. Here, when a marking having anappropriate size is not formed at the marking point mp (when the markingis small), a change in intensity of the reflected light at the markingpoint mp is small and a change in the optical reflection image is small.Therefore, an influence of the laser marking on the pattern image issmall. On the other hand, when a marking having an appropriate size isformed at the marking point mp, a change in at least one of a refractiveindex, a transmittance, an absorptivity, and a reflectance of lightbecomes large. As a result, the change in intensity of the reflectedlight at the marking point mp becomes large, and a mark image showingthe marking formed at the marking point mp appears on the pattern image.

For example, the analysis unit 21 c compares the pattern image (forexample, the pattern image A3) acquired before the laser marking withthe pattern image acquired after the laser marking and determineswhether a difference between the images is equal to or larger than apredetermined defined value. When the difference between the images isequal to or larger than the defined value (or larger than the definedvalue), the analysis unit 21 c determines that the mark image hasappeared (that is, a marking having an appropriate size has beenformed). On the other hand, when the difference between the images issmaller than the defined value (or equal to or smaller than the definedvalue), the analysis unit 21 c determines that the mark image has notappeared (that is, the marking having an appropriate size has not beenformed).

When the analysis unit 21 c determines that the mark image has appeared,the control unit 21 b records that the laser marking at the markingpoint mp is completed. The control unit 21 b determines whether or notscheduled laser marking of all marking points mp (for example, fourplaces in the embodiment) has been completed. When the laser marking ofall the marking points mp has been completed, the control unit 21 bcompletes the laser marking process. On the other hand, when markingpoints mp that have not been marked remain, the control unit 21 bperforms control so that the laser marking of the next marking point mpis started.

On the other hand, when the analysis unit 21 c determines that the markimage has not appeared, the control unit 21 b performs control so thatthe laser marking at the marking point mp is executed again. In thiscase, the control unit 21 b sets irradiation conditions of the laserlight output from the laser light source 16 in accordance with a size ofthe mark image (that is, a magnitude of the difference between theimages) detected by the analysis unit 21 c. That is, the control unit 21b calculates a necessary additional amount of irradiation with the laserlight to form a marking having a predetermined size in accordance with asize of the marking that has already been formed, and may setirradiation conditions in accordance with the amount of irradiation.

It should be noted that the determination in the analysis unit 21 cdescribed above may be executed by manual operation of the user. Forexample, the analysis unit 21 c may determine whether or not the markimage has appeared depending on input content from the user. In thiscase, the pattern image is displayed on the display unit 22. Informationon whether or not the mark image has appeared on the pattern image isinput to the input unit 23 by the user who visually confirms the patternimage. The input unit 23 outputs information indicating whether or notthe mark image has appeared to the computer 21. The analysis unit 21 cdetermines whether or not the mark image has appeared on the basis ofinformation indicating whether or not the mark image has appeared.

Further, when it is determined that the mark image has appeared, theanalysis unit 21 c compares the reference image A5 with the patternimage acquired after laser marking. When a point at which the mark hasbeen formed in the pattern image deviates from the marking point mp inthe reference image A5, the analysis unit 21 c determines that a markformation deviation occurs. In this case, control for correcting themarking point mp may be executed as follows. For example, the analysisunit 21 c notifies the control unit 21 b of information on the markformation deviation (for example, a direction of the deviation and amagnitude of the deviation). The control unit 21 b may perform positioncorrection by moving the XYZ stage 14 so that a mark is formed at thecorrect marking position mp on the basis of the information.

After the laser marking onto all the marking points mp has beencompleted as described above, the control unit 21 b operates the lightsource 12, the observation optical system 13A, and the photodetector 15.Accordingly, the photodetector 15 images the light from the light source12 reflected from the semiconductor device D, and outputs image data (adetection signal) to the analysis unit 21 c of the computer 21. Theanalysis unit 21 c generates a pattern image after laser marking (apattern image including a mark image) on the basis of the image data.

As illustrated in FIG. 5, the analysis unit 21 c can generate a markingimage A6 in which the mark image m and the fault point fp can bespecified, by superimposing the emission image on the pattern imageincluding the mark image. Here, the marking image A6 is an imagegenerated with the same magnification as the pattern image A3 with a lowmagnification. The analysis unit 21 c can acquire the marking positioninformation indicating a relative position of each mark image m withreference to the feature point P0 of the semiconductor device D bysuperimposing the marking image A6 and the pattern image A1 with a highmagnification on each other. For example, the analysis unit 21 c cancalculate a coordinate position of each mark image m when the coordinateposition of the feature point P0 is set as an origin position on thebasis of the image generated by superimposing the marking image A6 andthe pattern image A1 on each other as described above.

It should be noted that as described above, the laser marking iscontrolled so that the marking is formed at the marking point mp, andthe position of the mark image m and the position of the marking pointmp are matched with each other. Therefore, when accuracy of the markingposition by the laser marking is high (when an error between theposition of the mark image m and the position of the marking position mpis small), the analysis unit 21 c may calculate the coordinate positionof each marking point mp when the coordinate position of the featurepoint P0 is set as an origin position, on the basis of the imageobtained by superimposing the pattern image A1 and the reference imageA5 on each other.

Further, it is also preferable for the feature point P0 to be a pointindicating a feature pattern that can be specified not only from theback surface D1 side of the semiconductor device D but also from thefront surface D2 side. In this case, even when physical analysis isperformed on the semiconductor device D from the front surface D2 side,it is possible to easily specify the positions of the mark image m andthe fault point fp on the basis of the feature point P0. An example ofsuch a feature point P0 may be a corner portion of a memory mat.

The analysis unit 21 c stores the marking position information of themark image m (or the marking point mp) calculated as described above inthe storage medium included in the computer 21. It should be noted thatthe analysis unit 21 c may output the marking position information to arecording medium (for example, a USB memory) removable from the computer21 or may output the marking position information to an externalcomputer device via a wired or wireless communication network. Further,the analysis unit 21 c may output the marking position information tothe display unit 22. In this case, the display unit 22 may display themarking position information as a list or may display the markingposition information together with the marking image. Further, thesepieces of information may be output on a paper medium by an externaldevice such as a printer or the like.

Next, an example of an operation of the inspection device 1 from specifyof a fault point to output of marking position information will bedescribed with reference to FIG. 6.

First, the inspection device 1 inspects the semiconductor device D byexecuting the fault point specifying process described above, andspecifies the fault point fp in the semiconductor device D (step S1).Specifically, the inspection device 1 controls the XYZ stage 14 so thata field of view of the observation optical system 13A is located in anarea to be observed. The inspection device 1 controls the XYZ stage 14so that a focus of the objective lens matches the area to be observed.When the field of view of the observation optical system 13A is locatedin the area to be observed, the inspection device 1 irradiates thesemiconductor device D with the light output from the light source 12from the back surface D1 side of the semiconductor device D by theobservation optical system 13A, and acquires the optical reflectionimage generated by the photodetector 15. Subsequently, the inspectiondevice 1 applies a stimulation signal to the semiconductor device Dusing the stimulation device 11, and acquires an emission image usingthe photodetector 15. The inspection device 1 superimposes the acquiredoptical reflection image and the emission image on each other togenerate the analysis image A4 (see a portion (a) of FIG. 3), andspecifies the fault point fp on the basis of the analysis image A4.

Subsequently, the marking point mp is set in accordance with theposition of the fault point fp, and a reference image A5 is generated byadding a mark indicating the fault point fp and the marking point mp tothe analysis image A4. The control unit 21 b of the computer 21 movesthe XYZ stage 14 to a position in accordance with the marking point mp.Accordingly, the marking optical system 13B placed on the XYZ stage 14moves to an appropriate position in accordance with the marking point mp(step S2).

Subsequently, the control unit 21 b irradiates the semiconductor deviceD with laser light having a wavelength that is transmitted through thesubstrate SiE from the substrate SiE side so that a marking is formed atthe boundary between the substrate SiE and the metal layer ME at themarking point mp. Specifically, the control unit 21 b controls theoutput of the laser light source 16 on the basis of the laser lightirradiation condition set in advance as described above, therebyexecuting the irradiation of the marking point mp with the laser light(step S3). When the irradiation with the laser light based on theirradiation condition described above is completed in step S3, thecontrol unit 21 b stops the output of the laser light source 16,performs switching from the marking optical system 13B to theobservation optical system 13A, and starts the output of the lightsource 12. Accordingly, the photodetector 15 images the light from thelight source 12 reflected from the semiconductor device D, and outputsthe image data (the detection signal) described above to the analysisunit 21 c of the computer 21. The analysis unit 21 c generates a patternimage on the basis of the image data.

Subsequently, the analysis unit 21 c determines whether or not the markimage has appeared on the pattern image (step S4). When it is determinedthat no mark image has appeared on the pattern image (step S4: NO), theprocess of step S3 is executed again. On the other hand, when it isdetermined that the mark image has appeared on the pattern image (stepS4: YES), the control unit 21 b determines whether or not the markingpoint mp in which laser marking is not performed remains (step S5). Whenit is determined that a marking point mp at which laser marking is notperformed remains (step S5: YES), the process of step S2 is executed forthe remaining marking point mp. On the other hand, when it is determinedthat there is no marking point mp at which laser marking is notperformed (that is, laser marking at all marking points mp has beencompleted) (step S5: NO), the laser marking process is completed.

Subsequently, the analysis unit 21 c records the marking positioninformation (step S6). Specifically, the analysis unit 21 c generatesthe marking image A6 (see FIG. 5) which is a pattern image (a patternimage including a mark image) after completion of laser marking.Further, the analysis unit 21 c calculates a coordinate position of eachmark image m when the coordinate position of the feature point P0 is setas an origin position on the basis of the image (see FIG. 5) generatedby superimposing the marking image A6 and the pattern image A1.Accordingly, information indicating a relative position with respect tothe feature point P0 of each mark image in is obtained as markingposition information for specifying a position of the marking. Theanalysis unit 21 c stores the marking position information obtained thusin the storage medium included in the computer 21.

Subsequently, the analysis unit 21 c outputs the marking positioninformation (step S7). Specifically, the analysis unit 21 c may outputthe marking position information to a portable recording medium such asa USB memory as described above or may output the marking positioninformation to an external computer device (for example, an analysisdevice that performs physical analysis of the semiconductor device D).

Next, examples of a structure of the semiconductor device D and a placeat which a marking M is formed in each example will be described withreference to FIGS. 7 and 8. A portion (a) of FIG. 7 illustrates aschematic cross section of a semiconductor device 100 which is a logicdevice, a portion (b) of FIG. 7 illustrates a schematic cross section ofa semiconductor device 200 which is a memory device, and a portion (a)of FIG. 8 illustrates a schematic cross section of a semiconductordevice 300 which is a power device. Each of the semiconductor devices100, 200, and 300 includes a transistor layer T at a boundary between ametal layer ME and a substrate SiE. The transistor layer T includes acircuit element (for example, a gate element) embedded in at least oneof the metal layer ME and the substrate SiE at the boundary between themetal layer ME and the substrate SiE. In addition, the metal layer MEincludes a wiring layer provided with a wiring W electrically connectedto the transistor layer T on the front surface D2 side relative to thetransistor layer T. As illustrated in FIGS. 7 and 8, the marking M isformed mainly in the transistor layer T located at the boundary betweenthe substrate SiE and the wiring layer using the laser marking describedabove.

Here, as illustrated in FIGS. 8 and 9, the substrate SiE may be thinnedand the semiconductor device D may be observed from the thinnedsubstrate SiE side (the back surface D1 side) in physical analysis afterlaser marking. Here, FIG. 9 is a view illustrating a state after thesubstrate SiE of the semiconductor device 300 illustrated in FIG. 8 isthinned. As described above, the marking M is formed in the transistorlayer T which is the boundary between the substrate SiE and the metallayer ME. Therefore, it is possible to easily confirm the marking M fromthe back surface D1 side (see a portion (b) of FIG. 9) using an electronbeam (EB) or the like by thinning the substrate SiE by abrading thesubstrate SiE from the back surface D1 side. Accordingly, it is possibleto accurately perform the physical analysis on the basis of a positionof the marking. It should be noted that, in this example, a thickness d1of the substrate SiE before thinning is about 100 μm to 700 μm, and athickness d2 of the substrate SiE after thinning is about 10 μm.Further, when the substrate SiE is thinned to the thickness d2 of about1 μm, the marking M is likely to be confirmed using visible light.

FIG. 10 is a view illustrating an example of an SEM image showing themarking M formed between the substrate and the metal layer of thesemiconductor device that is a flash memory (a memory device) using theinspection method that is executed by the inspection device 1. A portion(a) of FIG. 10 illustrates an image with a low magnification(magnification: 30000) obtained by imaging a cross-sectional portionincluding the marking M in the semiconductor device using a scanningelectron microscope (SEM). A portion (b) of FIG. 10 illustrates an imagewith a high magnification (magnification: 60000) obtained by imaging thecross-sectional portion including the marking M in the semiconductordevice using the SEM.

Next, effects of the inspection device 1 and the inspection method thatis executed by the inspection device 1 will be described.

In the inspection device 1 and the inspection method, the semiconductordevice D is irradiated with laser light having a wavelength transmittedthrough the substrate SiE from the substrate SiE side so that a markingis formed at least at the boundary between the substrate SiE and themetal layer ME on the basis of the fault point fp (a predeterminedposition) specified in the semiconductor device D. It is possible toform the marking at a position at which the marking can be easilyconfirmed from both the front surface D2 side (the metal layer ME side)and the back surface D1 side (the substrate SiE side) by forming themarking at the boundary between the substrate SiE and the metal layerME. Accordingly, when laser marking is performed from the substrate SiEside of the semiconductor device D, it is possible to easily confirm themarking position from both the front surface D2 side and the backsurface D1 side at the time of physical analysis.

Further, the control unit 21 b controls the output of the laser lightsource 16 so that the marking does not penetrate through the metal layerME. Accordingly, the marking can be kept inside the semiconductor deviceD. As a result, it is possible to prevent the front surface D2 of thesemiconductor device D from being contaminated due to debris of thesemiconductor device D that may be generated at the time of markingformation. Further, the control unit 21 b controls the output of thelaser light source so that at least one of cavities, reforming, andmelting is generated as the marking. Thus, the marking can beappropriately formed.

Further, the inspection device 1 includes the analysis unit 21 c thatacquires a pattern image (for example, the marking image A6 describedabove) of the semiconductor device D including the mark image mindicating the marking on the basis of the detection signal.Accordingly, it is possible to acquire a pattern image from which themarking position can be visually ascertained together with the pattern(for example, a wiring pattern) of the semiconductor device D. With sucha pattern image, it becomes possible to easily ascertain the markingposition in the physical analysis.

The analysis unit 21 c acquires marking position information forspecifying the position of the marking on the basis of the patternimage, and outputs the marking position information. Accordingly, it ispossible to output the marking position information for specifying themarking position in the physical analysis to an external device or thelike. Therefore, for example, even in a case in which the inspectiondevice 1 that performs marking and the analysis device that performsphysical analysis are disposed in different places, it is possible toappropriately transfer the marking position information necessary toperform physical analysis to the analysis device.

The analysis unit 21 c acquires information indicating the relativeposition of the marking with reference to the feature point PO of thesemiconductor device D as the marking position information. It becomespossible to accurately ascertain the position of the marking by usingthe relative position of the marking with respect to the position of thefeature point P0 (for example, a groove portion of the wiring pattern)of the semiconductor device D as the marking position information inthis way.

Although the embodiment of the present invention has been describedabove, the present invention is not limited to the above embodiment. Forexample, in the above embodiment, the marking is formed at the faultpoint fp of the semiconductor device D specified by inspecting thesemiconductor device D, but the position at which the marking is formedis not limited to the fault point fp. That is, in the inspection device1, the semiconductor device D may be irradiated with laser light havinga wavelength transmitted through the substrate SiE from the substrateSiE side so that the marking is formed at least at the boundary betweenthe substrate SiE and the metal layer ME with respect to a predeterminedposition of the semiconductor device D. With such a configuration, amarking forming method for performing laser marking on the semiconductordevice D having the substrate SiE and the metal layer ME formed on thesubstrate SiE is realized. Further, in the inspection device 1,configurations of Modification example 1 to Modification example 4 to bedescribed below may be adopted.

MODIFICATION EXAMPLE 1

The inspection device 1 may include an infrared camera instead of thetwo-dimensional camera described above, as the photodetector 15. In thiscase, the inspection device 1 may not include the light source 12. Inaddition, since the light source 12 is not included, the observationoptical system 13A may not include the beam splitter. The infraredcamera images heat rays from the semiconductor device D to generate ameasurement image. It is possible to specify a heat generation place inthe semiconductor device D using an infrared image in accordance withthe measurement image. It is possible to specify the fault point of thesemiconductor device D by specifying the heat generation place. In acase in which the heat rays are measured, an InSb camera or the like isused as an infrared camera. It should be noted that the heat rays arelight having a wavelength of 2 μm to 10 μm. Further, it is possible toacquire an image showing a distribution of emissivity of thesemiconductor device D by imaging the heat rays from the semiconductordevice D.

In Modification example 1, the analysis unit 21 c of the computer 21generates an infrared image on the basis of the measurement imagedescribed above. Further, the analysis unit 21 c generates a patternimage on the basis of the detection signal. The analysis unit 21 cgenerates a superimposed image in which the infrared image issuperimposed on the pattern image, as an analysis image. A process ofspecifying the fault point from the analysis image is the same as in theabove embodiment.

A procedure of measuring the heat rays from the semiconductor device Dusing the infrared camera and generating the infrared image in theanalysis unit 21 c will be described in detail. First, in a state inwhich a stimulation signal such as a test pattern is being applied bythe stimulation device 11, a first measurement image including heatgeneration of the semiconductor device D is acquired by the infraredcamera. This first measurement image is generated by a plurality ofpieces of image data continuously captured in a predetermined exposuretime being transmitted to the computer 21 and added by the analysis unit21 c. The first measurement image has both the heat generation of thesemiconductor device D and information on shapes of elements forming thesemiconductor device D. Then, in a state in which the application of thestimulation signal by the stimulation device 11 is stopped, a secondmeasurement image including only the information on the shapes of theelements form the semiconductor device D is acquired by the infraredcamera. The second measurement image is generated by a plurality ofpieces of image data continuously captured in a predetermined exposuretime being transmitted to the computer 21 and added by the analysis unit21 c, similar to the first measurement image. The second measurementimage has only the information on the shapes of the elements forming thesemiconductor device D. The analysis unit 21 c performs a process ofsubtracting the second measurement image from the first measurementimage to generate an infrared image including only the heat generationof the semiconductor device D. The analysis unit 21 c generates thesecond measurement image as the pattern image using a superimposed imageobtained by superimposing the infrared image on the second measurementimage or the first measurement image as the analysis image. The processof specifying the fault point from the analysis image is the same as inthe above embodiment.

In the process of confirming the presence or absence of a mark imageafter laser marking, the observation optical system 13A transmits theheat rays from the semiconductor device D to the infrared camera. Theinfrared camera detects the heat rays and outputs image data (adetection signal) to the computer 21. The analysis unit 21 c generates apattern image based on the image data, as described above. A processafter the pattern image is generated is the same as in the embodimentdescribed above.

Modification Example 2

The inspection device 1 may include a power supply that is electricallyconnected to the semiconductor device D and applies a voltage to thesemiconductor device D, as the stimulation device 11. In addition, thelight output from the light source 12 may be coherent light such aslaser light. As the light source 12 that outputs coherent light, a solidlaser light source, a semiconductor laser light source, or the like canbe used. In a case in which an optical beam induced resistance change(OBIRCH) image, a soft defect localization (SDL) image, and the like areacquired, the light source 12 outputs laser light in a wavelength rangein which the semiconductor device D does not generate charge (carriers).For example, in a case in which the substrate SiE is made of silicon,the light source 12 outputs laser light having a wavelength rangegreater than 1200 nm and, preferably, about 1300 nm. Further, in a casein which the OBIC image, a Laser assisted device alteration (LADA)image, and the like is acquired, the light source 12 is required tooutput light in a wavelength range in which the semiconductor device Dgenerates charge (carriers), and therefore, the light source 12 outputslight having a wavelength range of 1200 nm or less (for example, laserlight having a wavelength range of about 1064 nm). The light output fromthe light source 12 may be incoherent light. As the light source 12 thatoutputs incoherent light, a super luminescent diode (SLD), an amplifiedspontaneous emission (ASE), a light emitting diode (LED), or the likecan be used. The light output from the light source 12 is guided to theobservation optical system 13A via a polarization preserving single modeoptical coupler and a polarization preserving single mode optical fiberfor probe light, and irradiated on the semiconductor device D. InModification example 2, the observation optical system 13A includes anoptical scanning unit and an objective lens. The optical scanning unitscans an irradiation spot on the back surface D1 of the semiconductordevice D. The optical scanning unit includes, for example, opticalscanning elements such as a galvanometer mirror, a polygon mirror, andan MEMS mirror. The objective lens condenses the light guided by theoptical scanning unit onto the irradiation spot.

In Modification example 2, the inspection device 1 may include anelectric signal detector electrically connected to the semiconductordevice D. The electric signal detector detects an electric signalgenerated in the semiconductor device D in accordance with laser light.The electric signal detector outputs an electric signal feature value inaccordance with the detected electric signal to the computer 21.Further, in Modification example 2, the photodetector 15 may include anoptical sensor. The optical sensor detects reflected light of thesemiconductor device D in accordance with the laser light and outputs adetection signal to the computer 21. The optical sensor is, for example,a photodiode, an avalanche photodiode, a photomultiplier tube, an areaimage sensor.

The analysis unit 21 c of the computer 21 generates an electric signalimage converted from the electric signal feature value in associationwith a scanning position of the laser light in accordance with theoptical scanning unit that is controlled by the control unit 21 b.Further, the analysis unit 21 c generates an optical reflection image onthe basis of the detection signal. The analysis unit 21 c generates asuperimposed image obtained by superimposing the electric signal imageon the optical reflection image, as the analysis image. A process ofspecifying the fault point from the analysis image is the same as in theembodiment described above.

The electric signal image is, for example, an OBIC image which is aphotovoltaic current image, an OBIRCH image which is an electricquantity change image, an SDL image which is an errata informationimage, and an LADA image. The OBIC image is an image obtained bydetecting a photovoltaic current generated due to laser irradiation andconverting a current value or a current change value of the photovoltaiccurrent into an image as an electric signal feature value. The OBIRCHimage is an image obtained by changing a resistance value at anirradiation position in the semiconductor device D through laserirradiation in a state in which a constant current is applied to thesemiconductor device D and converting a voltage value or a change valueof a voltage in accordance with the change in the resistance value as anelectric signal feature value into an image. It should be noted that theOBIRCH image may be an image obtained by changing a resistance value atan irradiation position in the semiconductor device D through laserirradiation in a state in which a constant voltage is applied to thesemiconductor device D and converting a change value of a current inaccordance with the change in the resistance value as an electric signalfeature value into an image. The SDL image is an image obtained bydetecting a malfunction state by irradiating the semiconductor device Dwith a laser having a wavelength at which carriers are not excited in astate in which a stimulation signal such as a test pattern is applied tothe semiconductor device D, converting information on the malfunctionstate (for example, a PASS/FAIL signal) as an electric signal featurevalue into a luminance count, and converting the luminance count into aninformation image. The LADA image is an image obtained by detecting amalfunction state by irradiating the semiconductor device D with a laserhaving a wavelength at which carriers are excited in a state in which astimulation signal such as a test pattern is applied to thesemiconductor device D, converting information on the malfunction state(for example, a PASS/FAIL signal) as an electric signal feature valueinto a luminance count, and converting the luminance count into aninformation image.

In the process of confirming the presence or absence of a mark imageafter laser marking, the light source 12 outputs light with which theback surface D1 side of the semiconductor device D is irradiated. Theobservation optical system 13A irradiates the back surface D1 of thesemiconductor device D with the light output from the light source 12.The observation optical system 13A transfers reflected light from thesemiconductor device D in accordance with the irradiated light to thephotodetector 15 which is an optical sensor. The optical sensor detectsthe reflected light and outputs a detection signal to the computer 21.The analysis unit 21 c generates a pattern image which is an opticalreflection image based on the detection signal. A process after thepattern image is generated is the same as in the embodiment describedabove.

MODIFICATION EXAMPLE 3

The inspection device 1 may specify a fault position using an opticalprobing technique called EOP or electro-optical frequency mapping(EOFM).

In Modification example 3, the semiconductor device D is scanned withthe light from the light source 12, and the reflected light from thesemiconductor device D is detected by the photodetector 15 which is anoptical sensor. The reflected light is output to the computer 21, and anoptical reflection image is generated by the analysis unit 21 c. Then,in a state in which a stimulation signal such as a test pattern isrepeatedly applied from the stimulation device 11 to the semiconductordevice D, an irradiation spot selected by a user on the basis of theoptical reflection image displayed on the display unit 22 and input bythe input unit 23 is irradiated with the light output from the lightsource 12. A wavelength of the light output from the light source 12 is,for example, 530 nm or more and, preferably, 1064 nm or more. Thereflected light modulated in accordance with an operation of elements inthe semiconductor device D is detected by the optical sensor and outputto the computer 21 as a detection signal. In the analysis unit 21 c, asignal waveform is generated on the basis of the detection signal, anddisplayed on the display unit 22. The optical reflection image describedabove can be used as an analysis image by looking for the fault pointfrom the signal waveform observed while changing the irradiation spot onthe basis of the optical reflection image described above.

Further, the analysis unit 21 c may generate an electro-optic frequencymapping image (EOFM image) by converting phase difference informationbetween the detection signal and the stimulation signal such as the testpattern into an image in association with an irradiation position. Inthis case, the phase difference information can be obtained from an ACcomponent extracted from the detection signal. Further, the opticalreflection image can be obtained by converting a DC component extractedsimultaneously with the AC component into an image in association withthe irradiation position. A superimposed image in which the EOFM imageis superimposed on the optical reflection image can be used as ananalysis image.

MODIFICATION EXAMPLE 4

The inspection device 1 may specify the fault position using amagneto-optical probing technique. In this case, the inspection device 1includes a magneto-optic crystal (MO crystal). In addition, theobservation optical system 13A includes a light splitting opticalsystem. The magneto-optical crystal is configured to be arbitrarilydisposed with respect to the semiconductor device D. First, in theinspection device 1, it is possible to generate the optical reflectionimage as in Modification example 2 and Modification example 3 byperforming switching to a configuration in which the magneto-opticalcrystal is not disposed between the objective lens and the semiconductordevice D. Then, switching to a configuration in which themagneto-optical crystal is disposed between the objective lens and thesemiconductor device D is performed, and the magneto-optical crystal isbrought into contact with the semiconductor device D to which astimulation signal such as a test pattern has been applied. Themagneto-optic crystal is irradiated with the light from the light source12 via the beam splitting optical system and the optical scanning unit,and reflected light is detected by the photodetector 15 which is anoptical sensor. In the semiconductor device D, when a current flows dueto the application of the stimulation signal such as a test pattern, asurrounding magnetic field changes and a polarization state of lightreflected by the magneto-optic crystal changes. The light of whichintensity has been changed in accordance with the change in thepolarization state is input to the optical sensor via the lightsplitting optical system. Thus, the light of which the intensity hasbeen changed in accordance with the change in the polarization state isdetected by the optical sensor and output as the detection signal to thecomputer 21, thereby generating a magneto-optical image. A superimposedimage in which the magneto-optical image is superimposed on the opticalreflection image may be used as the analysis image.

REFERENCE SIGNS LIST

-   -   1 Inspection device    -   12 Light source    -   13A Observation optical system    -   13B Marking optical system    -   15 Photodetector    -   16 Laser light source    -   21 b Control unit (marking control unit)    -   21 c Analysis unit (processing unit)    -   D Semiconductor device    -   ME Metal layer    -   SiE Substrate

1. An inspection method of performing laser marking on a semiconductordevice including a substrate and a metal layer formed on the substrate,the inspection method comprising: specifying a predetermined position inthe semiconductor device by inspecting the semiconductor device; andirradiating the semiconductor device with laser light having awavelength that is transmitted through the substrate from the substrateside so that a marking is formed at least at a boundary between thesubstrate and the metal layer on the basis of the predeterminedposition.
 2. The inspection method according to claim 1, wherein theirradiating the semiconductor device with the laser light includescontrolling the irradiation with the laser light so that the markingdoes not penetrate the metal layer.
 3. The inspection method accordingto claim 1, wherein the irradiating the semiconductor device with thelaser light includes controlling the irradiation with the laser light sothat at least one of cavities, reforming, and melting is generated asthe marking.
 4. The inspection method according to claim 1, furthercomprising acquiring a pattern image of the semiconductor deviceincluding a mark image indicating the marking.
 5. The inspection methodaccording to claim 4, further comprising: acquiring position informationfor specifying a position of the marking on the basis of the patternimage; and outputting the position information.
 6. The inspection methodaccording to claim 5, wherein the acquiring the position informationincludes acquiring information indicating a relative position of themarking with reference to a feature point of the semiconductor device asthe position information.
 7. The inspection method according to claim 1,further comprising thinning the substrate after the irradiating thesemiconductor device with the laser light, and observing thesemiconductor device from the thinned substrate side.
 8. An inspectiondevice that performs laser marking on a semiconductor device including asubstrate and a metal layer formed on the substrate, the inspectiondevice comprising: an observation optical system configured to transferlight from the substrate side of the semiconductor device; aphotodetector configured to detect light from the semiconductor devicevia the observation optical system and output a detection signal; alaser light source configured to output laser light having a wavelengththat is transmitted through the substrate; a marking optical systemconfigured to irradiate the semiconductor device with the laser lightoutput by the laser light source from the substrate side; and a markingcontroller configured to control an output of the laser light source sothat a marking is formed at least on a boundary between the substrateand the metal layer on the basis of a predetermined position that isspecified on the basis of the detection signal.
 9. The inspection deviceaccording to claim 8, wherein the marking controller controls the outputof the laser light source so that the marking does not penetrate throughthe metal layer.
 10. The inspection device according to claim 8, whereinthe marking controller controls the output of the laser light source sothat at least one of cavities, reforming, and melting is generated asthe marking.
 11. The inspection device according to claim 8, furthercomprising a processor configured to acquire a pattern image of thesemiconductor device including a mark image indicating the marking onthe basis of the detection signal.
 12. The inspection device accordingto claim 11, wherein the processor acquires position information forspecifying the position of the marking on the basis of the patternimage, and outputs the position information.
 13. The inspection deviceaccording to claim 12, wherein the processor acquires informationindicating a relative position of the marking with reference to afeature point of the semiconductor device as the position information.14. A marking forming method of performing laser marking on asemiconductor device including a substrate and a metal layer formed onthe substrate, the marking forming method comprising: irradiating thesemiconductor device with laser light having a wavelength that istransmitted through the substrate from the substrate side so that amarking is formed at least at a boundary between the substrate and themetal layer with respect to a predetermined position of thesemiconductor device.
 15. The marking forming method according to claim14, wherein the irradiating the semiconductor device with the laserlight includes controlling the irradiation with the laser light so thatthe marking does not penetrate the metal layer.
 16. The marking formingmethod according to claim 14, wherein the irradiating the semiconductordevice with the laser light includes controlling the irradiation withthe laser light so that at least one of cavities, reforming, and meltingis generated as the marking.